Mannesmann Aktiengesellschaft

Willi Weingarten

Heinz Schneider

Wolfgang Boettger

Friedhelm Schlawne

Wolfgang Bottger

Electrically conductive work pieces such as steel tubes or pipes are tested by means of a transducer comprised of a row of magnetic pole pieces through which a dc flux pattern of alternating polarity and direction is set up along a line of pole extensions and through which bidirectional ac ultrasonic transmission takes place to discover defects which return ultrasonic pulses.

Nondestructive testing

An electrodynamic transducing device includes two staggerdly coils with a distance of staggering equal to a quarter of a wavelength of ultrasonic waves; unidirectional transmission characteristics of the transducer is obtained by feeding the two coils separately with HF current at a time difference of feeding of the respective two signals to be equal to a quarter of the wavelength such that a reinforcing ultrasonic signal is produced in the direction of the coil receiving said signal earlier in time and complete cancelation of acoustic waves obtains in the opposite direction, whereby in case of equal pitch of said coils the HF signals are of equal contour but of opposite polarity while in case of opposite winding pitch the signals not only have equal signal contour but also the same polarity.

Electrodynamically producing ultrasonic waves

The invention relates to a method for the interference-free testing with guided waves for faults, through cyclic production and reception of ultrasonic waves, through assessment of the received HF-signals for signal components, which derive from faults and through evaluation of the result. In order to reliably improve the capabiliy of assessing the received HF-signal over the greatest possible lengths covered and thereby to enable the testing for faults to be carried out at a high speed and a high degree of reliability, it is proposed that the received HF-signals are digitalized within the cycle and that from the digital HF-signals of several successive cycles average values are formed and these are likewise rectified with the aid of a computer and in each case are filtered and assessed with a threshold value characteristic and if required a signal analysis for faults in the testing path.

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Krefeld, Germany

Willi Weingarten